Ground fault circuit interrupting (GFCI) devices, as currently available, are capable of interrupting fault current in the range of 4 to 6 milliamps. Circuits for such devices are described in U.S. Pat. Nos. 4,345,289 and 4,348,708, both of which are in the name of Edward K. Howell. The circuits described therein basically include a current sensor or magnetics, a signal processor or electronics and an electronic switch. The magnetics consist of a differential current transformer which responds to a current imbalance in the line and neutral conductors of the distribution circuit. This current imbalance is amplified by the signal processor pursuant to triggering the electronic switch and thereby complete an energization circuit for the trip solenoid. The current sensor also includes a neutral excitation transformer for responding to a ground fault on the neutral conductor.
A mounting arrangement for the GFCI device is described in U.S. Pat. Nos. 3,950,677 and 4,001,652 to Keith W. Klein et al. In the Klein et al GFCI device, the signal processor electronics is carried on a printed wire board and is positionally mounted and retained in one shell compartment of a GFCI receptacle casing. The magnetics are positionally mounted in another shell compartment within the receptacle and are locked in place by the insertion of single turn transformer winding elements. This GFCI assembly, although compact, does not readily lend to a fully automated assembly process since the magnetics contain two separate transformers which require electrical interconnection with each other as well as with the circuit electronics. To date, the electrical interconnection of the magnetics with the electronics has accounted for a good percentage of the time involved in the GFCI assembly process.
The operating mechanism for the Klein et al GFCI device is described within U.S. Pat. No. 4,010,432, also in the name of Keith W. Klein et al. This patent shows the arrangement between the latch and trip solenoid for tripping the device and deenergizing the receptacle sockets. Reference should be made to this patent for a detailed explanation of the state of the art of GFCI operating mechanisms as illustrated therein.
The purpose of this invention is to provide a compact operating mechanism which allows the interrupter contacts to be reset and latched upon depression of the reset button. The preassembly of a compact operating mechanism unit allows the unit to be robotically assembled within the GFCI case and fastened by means of a single retainer screw.